Silently ignore values and types with unsupported features.

driver/ocaml.prims

+Stdlib
 Stdlib.Buffer
 Stdlib.Bytes
 Stdlib.Char

ocamliface/mltypes.real.ml

@@ -230,6 +230,7 @@ let get_var id =
     vars := (id, i) :: !vars;
     i
 
+exception Skip
 let constr_table = Hashtbl.create 1024
 
 type env = { constrs : StringSet.t; seen : IntSet.t; vars : t IntMap.t }
@@ -247,8 +248,8 @@ let rec unfold_constr env p args =
     let k = (pn, args_id) in
     try Hashtbl.find constr_table k
     with Not_found ->
-      if StringSet.mem pn env.constrs then
-        failwith ("Polymorphic recursion forbidden : " ^ pn);
+      if StringSet.mem pn env.constrs then raise Skip
+        (*failwith ("Polymorphic recursion forbidden : " ^ pn)*);
       let slot = new_slot () in
       slot.recurs <- 1;
       Hashtbl.add constr_table k slot;
@@ -312,7 +313,7 @@ let rec unfold_constr env p args =
         | Type_abstract, Some t -> Link (unfold env t)
         | Type_abstract, None   -> (
             match args with [] -> Abstract pn | _l -> raise (PolyAbstract pn))
-        | Type_open, _          -> failwith "unsupported open type");
+        | Type_open, _          -> raise Skip);
       slot
 
 and unfold env ty =
@@ -349,7 +350,7 @@ and unfold env ty =
         try Link (IntMap.find ty.id env.vars)
         with Not_found -> Var (get_var ty.id))
     | Tconstr (p, args, _) -> Link (unfold_constr env p args)
-    | _ -> failwith "Unsupported feature");
+    | _ -> raise Skip);
   slot
 
 let unfold ty =
@@ -395,7 +396,7 @@ let values_of_sig name sg =
           match id.[0] with
           | 'a' .. 'z' | '_' -> (
               let n = name ^ "." ^ id in
-              try (n, fst (find_value n)) :: accu with PolyAbstract _ -> accu)
+              try (n, fst (find_value n)) :: accu with Skip | PolyAbstract _ -> accu)
           | _                -> accu
           (* operator *))
       | _ -> accu)
@@ -449,9 +450,11 @@ let read_cmi name =
         when Mlcompat.Mltypes.is_sig_value_val_reg s ->
           if not (Mlcompat.Mltypes.is_sig_value_deprecated s) then begin
             let id, t = Mlcompat.Mltypes.get_id_t_from_sig_value s in
+            try 
               let unf, n = unfold t in
               if n != 0 then unsupported "polymorphic value";
               values := (Ocaml.Ident.name id, t, unf) :: !values
+            with Skip -> ()
           end
       | Sig_type _ as s ->
           let id, t, rs = Mlcompat.Mltypes.get_sig_type s in